Wednesday 28 March 2012

First Flexing and More Knots

The latest Yew longbow is pretty well roughed out now so I put it on the tiller with a string just long enough to go on it and took it back to 50 pounds on the winch.
Note 50# on a slack string is substantially less than 50# on a braced bow (it probably equates to about 40... I did the experiment once but can't remember the exact figures... it's on the blog somewhere!).
It looked pretty reasonable and I gave it some flexing back and forth by pulling down on the string by hand whilst watching how it was bending.
Time to clean it up a bit and make sure the back is good and clean before proceeding.
As I inspected it I found a pin knot had popped out from the belly! This goes to show that my caution on the previous bow (from the same log) was fully justified. I inspected all the other knots and found 3 more which needed some excavation.
The first pic shows the popped pin, above it you can see another knot, which is shown from the other side in the next pic. Note, the W for 'Weak' pencilled on the limb (in both pics), this is how I mark any thin or weak spots so that I don't remove any more from there. The centreline marked on the back is also visible.
The second knot has been drilled right through with a 3mm drill, it drilled out some rather blackish stuff before getting down to sound wood, I also managed to snap the drill whilst trying to get it to go at the right angle to out in the right spot (it pulled out ok with a pair of pliers, as I hadn't been forcing it too hard).
You can also see how the sapwood is in a bit of a rough state, which is why I want to clean it up before I bend the bow too much.

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